JP4146442B2 - Load device - Google Patents

Description

  The present invention relates to a load device capable of adjusting impedance using electrical means such as a transistor, and more particularly to a load device used for a load test of a power supply device or a battery device.

In research and development and manufacturing inspection of power supply devices and battery devices, so-called load tests are indispensable for testing characteristics by setting various load impedances. In this load test, for example, an electronic load device that can arbitrarily adjust the impedance using a variable impedance element such as a transistor is widely used (see Patent Documents 1 to 4).
JP 2002-090404 A JP 2002-091577 A Japanese Patent No. 3470296 Japanese Patent No. 3477619

  In general, the current, voltage, and power ratings that can be driven in an electronic load device are the rating of the transistor used as a load (current rating, voltage rating, power rating, etc.) and the mechanism that discharges the heat generated in the transistor to the outside ( Heat sink and fan). In particular, the current and power ratings are dominated by the heat generated by the transistors, and in order to increase the ratings, it is necessary to increase the size of the heat sink or increase the number of transistors used.

Conventionally, the rating of the electronic load device is set based on the heat generated by the transistor when the load is continuously driven. For example, the current rating and power rating of an electronic load device are determined so that the transistor temperature does not exceed the temperature specified by the rating of the device when constant power is consumed under a certain environmental temperature. ing.
If the device is driven at a temperature exceeding this rated temperature, the characteristics of the transistor may deteriorate. Normally, the temperature of the transistor is monitored by a temperature sensor attached to a heat sink, etc. Is provided with a protection function that immediately cuts off the load current.

  On the other hand, recent electronic load devices have a function of simulating various waveforms of current. With this function, it is possible to simulate a pulsed load current flowing through, for example, a printer or a plasma display.

  When simulating a pulsed load, the electronic load device needs to flow a very large current instantaneously. However, the rating of the conventional electronic load device is determined on the assumption of steady load driving as described above, and even if it is instantaneous, a current exceeding the rating cannot flow. Therefore, when simulating such a pulse-shaped load, it is necessary to prepare an electronic load device having a very large rated value so that a large current and power at the peak value of the pulse can be steadily driven.

  For example, if the peak current of a pulse required for the test is 10 times the effective current, simply an electronic load device having a rated current 10 times the effective current must be prepared. In other words, an electronic load device having a rated power 10 times larger than the power consumed actually has to be prepared, and there is a disadvantage that the size of the device becomes unnecessarily large.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a load device capable of instantaneously testing a load having a large peak while suppressing an increase in the size of the device. is there.

According to the present invention, a load unit capable of controlling impedance, a detection unit for detecting at least one of the current, voltage and power of the load unit, and a signal corresponding to the temperature of the load unit, A signal generator that generates a plurality of upper limit setting signals for setting at least one upper limit of the current, voltage, and power of the load unit; and at least one of the current, voltage, and power of the load unit is the plurality of upper limit settings. A control unit that controls the impedance of the load unit so as not to exceed the upper limit set by the signal ,
The signal generation unit generates the plurality of upper limit setting signals according to a result obtained by integrating a difference between a detection value of the detection unit and a plurality of predetermined reference values with respect to time with different time constants;
A load device is provided.

Preferably, the apparatus includes a temperature sensor that converts the temperature of the load unit into an electrical signal and outputs the electric signal, and the signal generation unit has a lower upper limit when the temperature of the load unit increases, and the temperature of the load unit The predetermined reference value is set according to the output signal of the temperature sensor so that the upper limit becomes higher when the value becomes lower.

Preferably, the apparatus includes a temperature sensor that converts the temperature of the load unit into an electrical signal and outputs the electric signal, and the signal generation unit shortens the time constant when the temperature of the load unit increases, and the load unit The predetermined reference value is set according to the output signal of the temperature sensor so that the time constant becomes longer when the temperature of the temperature sensor becomes lower.

Preferably, the signal generation unit corrects the upper limit setting signal of the current and / or power of the load unit according to the voltage detected by the signal detection unit.

Preferably, when the signal generation unit sets the upper limit setting signal, an upper limit value indicated by the upper limit setting signal is adapted to a safe operation region of the variable impedance element of the load unit. Correcting the reference value according to the voltage detected by the detection unit;
Alternatively, the time constant is corrected according to the voltage detected by the detection unit,
Or, an offset is added to the upper limit setting signal according to the voltage detected by the detection unit,
Alternatively, the upper limit setting signal is multiplied by a proportional multiplier according to the voltage detected by the detection unit.

It is favored properly, the signal generation unit includes a first input terminal, a second input terminal, a first differential operational amplifier and an output terminal, a first of the first differential operational amplifier An input resistance element connected to the input terminal and configured to input a signal indicating power detected by the detection unit to the first input terminal, and connected to a second input terminal of the first differential operational amplifier, A reference voltage generation circuit that outputs a voltage corresponding to a reference power, and a capacitor provided between an output terminal of the first differential operational amplifier and the first input terminal;
The time constant is defined by the resistance value of the input resistance element and the capacitance value of the capacitor,
The first differential operational amplifier, the input resistance element, and the feedback capacitor cooperate to apply to the first input terminal and the second input terminal of the first differential operational amplifier. is the voltage difference amplified by calculating of, it generates the upper limit setting signal a difference signal obtained by the amplification by integrating with the time constant.

Preferably, the control unit includes a voltage generation circuit that generates a voltage for setting a target value of a load current of the power supply device, first and second input terminals, and the variable impedance included in the load unit. A second differential operational amplifier circuit having an output terminal connected to a control input terminal of the element; and an upper limit value of a voltage for setting a target value of the load current generated by the voltage generating circuit. A limit circuit that is limited according to the upper limit setting signal output from the signal generation unit and is input to the first input terminal of the second differential operational amplifier circuit, and a load unit capable of controlling the impedance A resistance element for detecting a current flowing in the variable impedance element included in
Connected to a second input terminal of the second differential operational amplifier circuit at a connection point between the resistance element and the output of the variable impedance element;
The transistor, the second differential operational amplifier circuit, and the resistance element constitute a constant current circuit,
The second differential operational amplifier circuit obtains a difference between an output signal of the limit circuit applied to the first input terminal and a terminal voltage of the resistance element applied to the second input terminal. Then, the amplified difference signal is applied to the control input terminal of the transistor.
Preferably, the detection unit includes a current detection unit that detects a current of the load unit, a voltage detection unit that detects a voltage of the load unit, a current detection signal by the current detection unit, and a voltage by the voltage detection unit. A multiplier that multiplies the detection signal to calculate power.

  According to the present invention, since at least one of the current, voltage and power of the load section is controlled so as not to exceed the upper limit set according to the temperature of the load section, it operates only within the range of the steady rating. Compared to the case where it is not possible, a large current, voltage, and power can be driven instantaneously.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a diagram illustrating an example of the configuration of the electronic load device according to the first embodiment of the present invention.
The electronic load device illustrated in FIG. 1 includes a load unit 2, a signal generation unit 3, a control unit 4, and a detection unit 5.
The load unit 2 is an embodiment of the load unit of the present invention. The signal generation unit 3 is an embodiment of the signal generation unit of the present invention. The control unit 4 is an embodiment of the control unit of the present invention. The detection unit 5 is an embodiment of the detection unit of the present invention.

  The load unit 2 is configured using a variable impedance element such as a transistor, for example, and changes the impedance in accordance with the control of the control unit 4. For example, as shown in FIG. 1, the load unit 2 is connected to a power supply device 1 to be tested. The power supply device 1 is a DC constant voltage power supply device, for example, and applies a constant DC voltage V to the load unit 2. The load unit 2 sets the load current I of the power supply device 1 to a desired value by changing the impedance according to the control of the control unit 4.

  The control unit 4 controls the impedance of the load unit 2. The control unit 4 includes a circuit that controls the current, voltage, power, resistance, and the like of the load unit by negative feedback, for example. The control unit 4 controls the impedance of the load unit 2 so that the current, voltage, power, resistance, and the like of the load unit 2 have desired values according to a command from a system controller (not shown), for example.

  The control unit 4 controls the upper limit of the current and power of the load unit 2 according to the upper limit setting signals L1 and L2 generated by the signal generation unit 3. That is, the impedance of the load unit 2 is controlled so that the current and power of the load unit 2 do not exceed the upper limit set by the upper limit setting signals L1 and L2.

FIG. 2 is a diagram illustrating an example of the configuration of the load unit 2 and the control unit 4.
In the example of FIG. 2, the load unit 2 includes an n-channel MOS transistor 21, and the control unit 4 includes an operational amplifier 41, a current detection resistor 42, a voltage generation circuit 43, a limit circuit 44, have.

  The drain of the MOS transistor 21 is connected to one positive output terminal of the power supply device 1, and its source is connected to the negative output terminal of the power supply device 1 via the resistor 42. The negative output terminal of the power supply device 1 is connected to the reference potential G.

The operational amplifier 41 has a positive input terminal connected to the voltage output of the voltage generation circuit 43 via the limit circuit 44, a negative input terminal connected to the source of the MOS transistor 21, and an output terminal connected to the gate of the MOS transistor 21. Is done.
The operational amplifier 41 amplifies the potential difference between the positive input terminal and the negative input terminal. When the positive input terminal has a higher potential than the negative input terminal, the operational amplifier 41 outputs a positive voltage with respect to the reference potential, and when the negative input terminal has a higher potential than the positive input terminal, A negative voltage is output with respect to the reference potential.

  The voltage generation circuit 43 generates a voltage Vset for setting a target value of the load current of the power supply device 1. The voltage generation circuit 43 changes the level of the output voltage Vset according to a command from a system controller (not shown), for example.

  The limit circuit 44 limits the upper limit value of the voltage input from the voltage generation circuit 43 to the positive input terminal of the operational amplifier 41 according to upper limit setting signals L1 and L2 generated in the signal generation unit 3 described later. That is, when the output voltage Vset of the voltage generation circuit 43 exceeds the lower one of the upper limit values of the voltages set by the upper limit setting signals L1 and L2, the limit circuit 44 is limited by the lower upper limit value. Is input to the positive input terminal of the operational amplifier 41.

In the circuit shown in FIG. 2, the MOS transistor 21, the operational amplifier 41, and the resistor 42 constitute a constant current circuit. That is, the gate voltage of the MOS transistor 21 is controlled so that the voltage generated in the resistor 42 by the load current I of the power supply device 1 and the voltage input to the positive input terminal of the operational amplifier 41 are substantially equal. The drain-source impedance of 21 is adjusted.
When the output voltage Vset of the voltage generation circuit 43 does not exceed the upper limit value set by the upper limit setting signals L1 and L2, a load current I corresponding to the output voltage of the voltage generation circuit 43 flows through the output of the power supply device 1.
On the other hand, when the output voltage Vset of the voltage generation circuit 43 exceeds the upper limit value set by the upper limit setting signals L1 and L2, the voltage input to the positive input terminal of the operational amplifier 41 is limited to this upper limit value. The load current I of the device 1 is also limited to a current corresponding to this upper limit value.
As described above, according to the circuit shown in FIG. 2, the load current I of the power supply device 1 is limited according to the upper limit setting signals L <b> 1 and L <b> 2 generated in the signal generator 3.

Returning to the description of FIG.
The detection unit 5 detects the current or power of the load unit 2.
In the example of FIG. 1, the detection unit 5 detects the power of the load unit. That is, the detection unit 5 illustrated in FIG. 1 includes a current detection unit 51 that detects a current of the load unit 2, a voltage detection unit 52 that detects a voltage of the load unit 2, and a multiplier 53. Multiplier 53 multiplies detection value Is of load current I in current detection unit 51 by detection value Vs of load voltage V in voltage detection unit 52, and outputs the multiplication result as detection value Ps of load power.

The signal generator 3 is a signal corresponding to the temperature of the load unit 2 and generates an upper limit setting signal for setting an upper limit of the current or power of the load unit 2.
In the example of FIG. 1, the signal generation unit 3 includes two integration circuits 31 and 32.
The integrating circuit 31 generates an upper limit setting signal L1 corresponding to the result of integrating the difference between the power detection value Ps of the detection unit 5 and the reference value P1 with the time constant τ1.
The integration circuit 32 generates an upper limit setting signal L2 corresponding to the result of integrating the difference between the power detection value Ps of the detection unit 5 and the reference value P2 (P2 <P1) with a time constant τ2 (τ2> τ1).

FIG. 3 is a diagram illustrating an example of the configuration of the integration circuit 31.
The integration circuit 31 illustrated in FIG. 3 includes an operational amplifier 311, a resistor 312, a capacitor 313, and a voltage generation circuit 314.

  A reference value P 1 generated by the voltage generation circuit 314 is input to the positive input terminal of the operational amplifier 311. The power detection value Ps is input to the negative input terminal of the operational amplifier 311 via the resistor 312 and the output voltage of the operational amplifier 311 is input via the capacitor 313. The output voltage of the operational amplifier 311 corresponds to the upper limit setting signal L1.

  According to the circuit shown in FIG. 3, when the output voltage of the operational amplifier 311 is not saturated with the positive or negative power supply voltage, negative feedback is performed so that the positive input terminal and the negative input terminal of the operational amplifier 311 have substantially the same voltage. Therefore, the difference voltage (Ps−P1) between the detected power value Ps and the reference value P1 is applied to the resistor 312. When the resistance value of the resistor 312 is ‘R1’, the current Ir1 of the resistor 312 is expressed by the following equation.

(Equation 1)
Ir1 = (Ps−P1) / R1 (1)

  Since the current Ir1 flows into the capacitor 313 as it is and charges the capacitor 313, assuming that the capacitance of the capacitor 313 is ‘C1’, the voltage Vc1 of the capacitor is expressed by the following time integration.

(Equation 2)
Vc1 = − (1 / τ1) × ∫ {(Ps−P1} dt (2)
τ1 = R1 × C1 (3)

  Therefore, the upper limit setting signal L1 is expressed by the following equation.

(Equation 3)
L = P1- (1 / τ1) × ∫ {(Ps−P1} dt (4)

  As described above, the upper limit setting signal L1 generated in the circuit shown in FIG. 3 is a signal corresponding to the result of integrating the difference between the power detection value Ps and the reference value P1 with the time constant τ1.

  FIG. 3 is a diagram illustrating an example of the configuration of the integration circuit 31, but the integration circuit 32 can also be configured using an operational amplifier, a resistor, and a capacitor, as in FIG.

Here, the operation of the electronic load device shown in FIG. 1 having the above-described configuration will be described.
FIG. 4 is a diagram illustrating the change over time of load power and the change over time of the temperature of the load unit 2 when the set value of the load current I is changed stepwise in the electronic load device shown in FIG.
FIG. 4A shows the change over time of the set value Vset of the load current (the output voltage of the voltage generation circuit 43 in FIG. 2). In the example of FIG. 4A, three patterns of waveform curves CV1 to CV3 rising in a step shape at time t0 are illustrated.
FIG. 4B shows a change in load power with time. The three negative overpower waveform curves CV4, CV5, and CV6 shown in FIG. 4B correspond to the three load setting value waveform curves CV1, CV2, and CV3 shown in FIG. 4A, respectively. In addition, when the power supply device 1 is a constant voltage power supply, the current I flowing through the load unit 2 changes with a tendency similar to that of the load power shown in FIG.
FIG. 4C shows a change over time in the temperature of the load section 2. The solid line indicates the change over time in the load temperature when the upper limit value of the load current I is limited according to the upper limit setting signals L1 and L2, and the dotted line indicates the time when the upper limit value is not limited.

When the load current I is set to a value larger than the steady rated current, if the current continues to flow without any limitation, the temperature of the load unit 2 will change as shown by the dotted line in FIG. The rating may be exceeded and circuit elements such as transistors may be deteriorated.
On the other hand, in the electronic load device according to the present embodiment, the upper limit setting signals L1 and L2 are generated so that the upper limit value of the load current decreases as the temperature of the load unit 2 increases. That is, when the detected value Ps of the load power becomes larger than the reference values P1 and P2, the upper limit setting signal is expressed by the relationship of the equation (4) according to the integration result of the difference between the detected value Ps and the reference values P1 and P2. The upper limit values of L1 and L2 decrease with time.

In FIG. 4B, the power value W1 corresponds to the reference value P1, and the power value W2 corresponds to the reference value P2.
When the detection value Ps of the load power input to the integration circuits 31 and 32 reaches the reference values P1 and P2, the time change of the upper limit setting signals L1 and L2 due to integration stops, so that the load power becomes the reference values P1 and P2. The corresponding power values W1 and W2 are stabilized.
In the signal generation circuit 3 shown in FIG. 1, since the constants of the integration circuits 31 and 32 are set so that the reference value is 'P1>P2' and the time constant is 'τ1 <τ2', the load power is the power value. When exceeding W1 and W2 (CV1 and CV4 in FIG. 4B), the load power is first stabilized at the power value W1 and then stabilized at the power value W2. That is, the load power decreases with time according to the time change of the upper limit setting signal L1, and is temporarily stabilized at the power value W1. Thereafter, the load power further decreases according to the time change of the upper limit value setting signal L2, and finally stabilizes at the power value W2. Thus, the load power changes in two stages according to the time change of the upper limit value setting signals L1 and L2.
On the other hand, when the load power exceeds only the power value W2 (CV2 and CV5 in FIG. 4B), the load power gradually decreases according to the upper limit setting signal L2 after a certain time has elapsed, and finally At the power value W2.
In addition, when the load power does not exceed both of the power values W1 and W2 (CV3 and CV6 in FIG. 4B), the load power rises at time t0 because the upper limit value setting signals L1 and L2 do not limit. Maintained in time.

As described above, in the electronic load device according to the present embodiment, when a load state occurs such that the temperature of the load unit 2 rises above the rated temperature (for example, the power of the load is set by the reference values P1 and P2). Upper limit setting signals L1 and L2 are generated so that the upper limit of the load power decreases in response to the temperature rise of the load unit 2, and the upper limit setting signals L1 and L2 are Thus, the current of the load unit 2 is limited. Therefore, even when a large load current is passed instantaneously, as shown in FIG. 4B, the temperature rise of the load unit 2 can be suppressed and the temperature can be prevented from reaching the rating.
In other words, according to the electronic load device according to the present embodiment, when the temperature of the load unit 2 still has a margin with respect to the rating, the current and power that are significantly larger than the conventional steady current and power ratings are driven. can do. Therefore, a very large load can be instantaneously driven without unnecessarily increasing the apparatus size.

In addition, when driving current / power with periodic peaks, conventional electronic load devices are not allowed to exceed a steady-state rating even instantaneously, so even though the effective current and average power are small. There was a restriction that the peak value of current and power could not be increased too much. On the other hand, in the electronic load device according to the present embodiment, as long as the temperature of the load unit 2 is within an allowable range, a large current / power exceeding a steady rating can be driven.
Therefore, according to the electronic load device according to the present embodiment, even when a load having a periodic peak is driven, a load having a very large peak value can be driven without unnecessarily increasing the device size. Can do.

  Next, some modified examples of the electronic load device according to the present embodiment will be described.

FIG. 5 is a diagram illustrating a first modification of the electronic load device according to this embodiment.
The electronic load device shown in FIG. 5 is obtained by replacing the signal generation unit 3 in the electronic load device shown in FIG. 1 with a signal generation unit 3A.

As shown in FIG. 5, the signal generation unit 3 </ b> A includes an integration circuit 33 in addition to the integration circuits 31 and 32 in the signal generation unit 3. The integration circuit 33 generates an upper limit setting signal L3 corresponding to the result of integrating the difference between the power detection value Ps of the detection unit 5 and the reference value P3 (P3 <P2 <P1) with a time constant τ3 (τ3>τ2> τ1). Generate.
The control unit 4 controls the impedance of the load unit 2 so that the current and power of the load unit 2 do not exceed the upper limits set by the upper limit setting signals L1, L2, and L3.

FIG. 6A is a diagram illustrating the change over time in load power when the set value of the load current I is changed stepwise in the electronic load device shown in FIG. In FIG. 6A, power values W1, W2, and W3 correspond to reference values P1, P2, and P3 of the integration circuit, respectively.
As can be seen by comparing FIG. 6 (A) and FIG. 4 (B), by providing three integration circuits having different reference values and time constants, the upper limit values of the current and power in the load unit 2 can be set as time. It is possible to reduce to three stages with the progress. If the number of integrating circuits is further increased, it is possible to realize a multistage time change.

  On the other hand, when the number of integrating circuits is reduced to one, for example, as shown in FIG. 6B, it is possible to widen the time range in which the upper limit value of the load current changes exponentially.

  Further, by appropriately setting the input / output characteristics of the signal generation unit, for example, as shown in FIGS. 6C and 6D, the upper limit values of the current and power in the load unit 2 can be changed into a polygonal line. Is possible.

The relationship between the current / power driven in the load unit 2 and the temperature generated in the load unit 2 is, for example, various factors such as the characteristics of the transistor serving as the load, the heat capacity of the heat sink, and the thermal resistance between the heat sink and the transistor. It can be defined by the transfer function determined by
Therefore, for example, if a signal generation unit having an appropriate characteristic corresponding to the above transfer function is selected from various characteristics as shown in FIGS. 6 (A) to (D), the temperature of the load unit 2 is rated. It is possible to drive a larger instantaneous load for a longer time without exceeding the temperature.

FIG. 7 is a diagram illustrating a second modification of the electronic load device according to this embodiment.
The electronic load device shown in FIG. 7 is obtained by replacing the signal generating unit 3 and the signal generating unit 3B in the electronic load device shown in FIG. 1 with the detecting unit 5B.

  The detection unit 5 </ b> B includes a current detection unit 51 that detects the current I of the load unit 2.

The signal generation unit 3B includes integration circuits 31B and 32B.
The integration circuit 31B generates an upper limit setting signal L1B according to the result of integrating the difference between the current detection value Is calculated by the detection unit 5B and the reference value I1 with a time constant τ1.
The integration circuit 32B generates an upper limit setting signal L2B corresponding to the result of integrating the difference between the current detection value Is and the reference value I2 (I2 <I1) with a time constant τ2 (τ2> τ1).

  According to the configuration described above, the upper limit setting signals L1B and L2B are generated according to the result of integrating the difference between the detected value Is of the load current I and the predetermined reference values I1 and I2 with the predetermined time constants τ1 and τ2. .

When the power supply device 1 to be tested is a constant voltage power supply, the output power is constant, so the load power is proportional to the effective value of the load current I. On the other hand, when the load current I does not contain much AC component and its time change is slow, the effective value of the load current I is substantially equal to the time average of the load current I. Therefore, when the time integral of the load power increases, the time integral of the current detection value Is similarly increases. When the time integral of the load power decreases, the time integral of the current detection value Is similarly decreases.
That is, when the power supply device 1 is a constant voltage power supply and the load current I does not include a lot of AC components, the upper limit setting signals L1B and L2B of the signal generation unit 3B generated according to the time integration of the current detection value Is are The upper limit setting signals L1 and L2 of the signal generation unit 3 generated according to the time integration of the load power and the temperature of the load unit 2 change with similar tendencies.

  Therefore, the electronic load device shown in FIG. 7 operates in the same manner as the electronic load device shown in FIG. 1, and it is possible to instantaneously drive a large load while suppressing the temperature rise of the load unit 2.

FIG. 8 is a diagram illustrating a second modification of the electronic load device according to this embodiment.
The electronic load device shown in FIG. 8 is obtained by replacing the signal generator 3 and the signal generator 3C in the electronic load device shown in FIG. 1 with the detector 5C.

  The detection unit 5C includes a current detection unit 51 that detects the current I of the load unit 2, and a multiplier 53 that squares the detection value Is.

The signal generation unit 3C includes integration circuits 31C and 32C.
Integrator circuit 31C generates the upper limit setting signal L1C corresponding to the result of integrating with the time constant τ1 of the difference between the detected portion square value of the current detection value Is calculated in the 5C Is ² and the reference value Iq1.
Integrator circuit 32C generates the upper limit setting signal L2C corresponding to the result of integrating the <time constant .tau.2 (.tau.2 the difference between (Iq1 .tau.1) square value Is ² and the reference value Iq2 Iq2)>.

According to the above-described configuration, the load current detection value Is a squared value Is ² with a predetermined reference value of I Iq1, Ip2 time constant τ1 of the difference between predetermined and, depending on the result of integrating with .tau.2, the upper limit setting signal L1C , L2C is generated.

When the power supply device 1 to be tested is a constant voltage power supply, the output power is constant, so the load power is proportional to the effective value of the load current I. On the other hand, the squared value of the effective value of the load current I is proportional to the result of integrating the squared value Is ² of the current detection value Is time. Therefore, when the time integral of the load power increases, the time integral of the square value Is ² also increases, and when the time integral of the load power decreases, the time integral of the square value Is ² also decreases.
That is, when the power supply device 1 is a constant voltage power supply, the upper limit setting signal L1C signal generator 3C generated according to the time integral of the square value Is ^2, L2C is generated according to the time integral of the load power The upper limit setting signals L1 and L2 of the signal generation unit 3 and the temperature of the load unit 2 are correlated with each other.

The effective value of the load current I is more precisely proportional to the square root of the result of integrating the square value Is ² of the current detection value Is time. Therefore, the signal generation unit 3C may further perform a square root calculation on the result of the time integration described above when generating the upper limit setting signals L1C and L2C. That is, the load current detection value Is value Is ² and the reference value obtained by squaring the I Iq1, Ip2 time constant τ1 of the difference between predetermined and integrates with .tau.2, the upper limit setting signal L1C according to the square root of the result of the integration, L2C May be generated.

  Therefore, the electronic load device shown in FIG. 8 operates in the same manner as the electronic load device shown in FIG. 1 and can instantaneously drive a large load while suppressing the temperature rise of the load unit 2.

FIG. 9 is a diagram illustrating a fourth modification of the electronic load device according to this embodiment.
The electronic load device shown in FIG. 9 is obtained by replacing the signal generation unit 3 in the electronic load device shown in FIG. 1 with a signal generation unit 3D and further providing a temperature sensor 6.

The temperature sensor 6 converts the temperature of the load unit 2 into an electrical signal and outputs it. For example, the temperature of a case of a transistor used as a variable impedance element in the load unit 2 or the temperature of a heat sink to which the transistor is attached is detected.
The temperature sensor 6 may be, for example, a measurement temperature resistor, a measurement temperature semiconductor, a thermocouple, or the like that is attached (or incorporated) in contact with the transistor of the load unit 2, or a sensor that detects infrared rays radiated from the transistor. But it ’s okay. Alternatively, the temperature may be detected using temperature characteristics such as a threshold value of a transistor.

The signal generation unit 3D includes integration circuits 31D and 32D that generate upper limit setting signals L1 and L2 similar to the signal generation unit 3 described above.
The integration circuits 31D and 32D are configured to change the reference values P1 and P2 in the integration circuits 31 and 32 according to the detection value Ts of the temperature sensor 6. For example, in FIG. 3, the voltage generation circuit 314 is configured such that the reference value P1 changes according to the temperature detection value Ts.

In the above-described electronic load device shown in FIGS. 1, 5, 7, and 8, for example, when the environmental temperature around the electronic load device is increased or when the load is driven, the temperature of the load unit 2 is increased. Even if the temperature rises, if the detection result of the detector 5 (5B, 5C) and the initial state of the integration circuit 31 are the same, the same upper limit setting signal is generated regardless of this temperature rise, and the load current is increased by the same upper limit value. Limited.
However, when the environmental temperature or the temperature of the load unit 2 is high, the heat generation of the load should be kept lower than when the temperature is low. For this purpose, the upper limit value by the upper limit setting signal is lowered or the upper limit value is increased. It is necessary to increase the speed of decrease in value. Therefore, in the electronic load device described above, it is necessary to anticipate the margin of the temperature change in advance and suppress the peak value of the instantaneous load and the performance of the driving time.

In contrast, in the electronic load device shown in FIG. 9, the reference values P <b> 1 and P <b> 2 change according to the detection value Ts of the temperature sensor 6. For example, when the detected temperature of the load unit 2 is high, the reference values P1 and P2 are lowered to lower the upper limit value of the load by the upper limit setting signal, and when the detected temperature of the load unit 2 is low, the reference value The values P1 and P2 are increased to increase the upper limit value of the load by the upper limit setting signal.
Therefore, according to the electronic load device shown in FIG. 9, the margin of temperature change can be reduced as compared with the electronic load device described above, so that a larger instantaneous load can be driven for a longer time. .

FIG. 10 is a diagram illustrating a fifth modification of the electronic load device according to this embodiment.
The electronic load device shown in FIG. 10 is obtained by replacing the signal generation unit 3 in the electronic load device shown in FIG. 1 with a signal generation unit 3E, and further providing a temperature sensor 6 similar to the electronic load device shown in FIG. is there.

The signal generation unit 3E includes integration circuits 31E and 32E that generate upper limit setting signals L1 and L2 similar to the signal generation unit 3 described above.
The integrating circuits 31E and 32E change the time constants τ1 and τ2 in the integrating circuits 31 and 32 in accordance with the detection value Ts of the temperature sensor 6. For example, in FIG. 3, the resistor 312 is replaced with a variable resistor so that the resistance value R1 of the resistor 312 changes according to the temperature detection value Ts.

In the electronic load device shown in FIG. 10, the time constants τ1, τ2 change according to the detection value Ts of the temperature sensor 6. For example, when the detected temperature of the load unit 2 is high, the reference value time constants τ1 and τ2 are shortened to increase the speed at which the upper limit value of the load is lowered by the upper limit setting signal. Is low, the time constants τ1, τ2 are lengthened to slow down the lowering of the upper limit value by the upper limit setting signal.
Thus, according to the electronic load device shown in FIG. 10, the margin of temperature change can be reduced as compared with the electronic load device described above, so that a larger instantaneous load can be driven for a longer time. Become.

FIG. 11 is a diagram illustrating a sixth modification of the electronic load device according to this embodiment.
The electronic load device shown in FIG. 11 is obtained by replacing the signal generation unit 3 in the electronic load device shown in FIG. 1 with a signal generation unit 3F.

The signal generation unit 3F includes integration circuits 31F and 32F that generate upper limit setting signals L1 and L2 similar to the signal generation unit 3 described above.
The integrating circuits 31F and 32F change the reference values P1 and P2 in the integrating circuits 31 and 32 in accordance with the detection value Vs of the voltage detection unit 52. For example, in FIG. 3, the voltage generation circuit 314 is configured such that the reference value P1 changes according to the detection value Vs.

  Thus, in the sixth modification of the electronic load device according to the present embodiment, the upper limit setting signals L1 and L2 are corrected according to the detection value Vs of the voltage detection unit 52.

Generally, in a variable impedance element such as a transistor, there is a certain relationship between the maximum value of current at which normal operation of the element is guaranteed and the voltage applied to the element.
When, for example, a MOS transistor is used as the variable impedance element of the load unit 2, the current rating of the load unit 2 is defined by the current rating of the MOS transistor. In the MOS transistor, for example, as shown in FIG. 12, a range (a safe operation region) of a drain current Id and a drain-source voltage Vds in which normal operation is guaranteed at a certain case temperature is defined. The rating of the drain current Id changes as a function of the drain-source voltage Vds, for example, as shown in FIG. When the drain-source voltage Vds is higher than a predetermined voltage, the current rating is reduced due to the limitation of the power rating.

  In the electronic load device shown in FIG. 11, the upper limit value setting signals L1 and L2 are corrected in consideration of such characteristics of the variable impedance element. For example, when the voltage of the load unit 2 becomes higher than a predetermined voltage, the upper limit value is set so that the upper limit value of the load current (or load power) becomes smaller according to the current rating of the variable impedance element (for example, MOS transistor). The setting signals L1 and L2 are corrected. In the example of FIG. 11, when the voltage detection value Vs becomes larger than a predetermined voltage, the reference values P1 and P2 are adjusted to be small.

FIG. 13 is a diagram illustrating an example of the configuration of the integration circuit 31F. An integration circuit 31F shown in FIG. 13 is obtained by replacing the voltage generation circuit 314 in the integration circuit 31 shown in FIG.
The voltage generation circuit 315 generates a predetermined reference value P1 when the voltage detection value Vs of the load is lower than a predetermined voltage. When the voltage detection value Vs becomes higher than the predetermined voltage, for example, according to a broken line function as shown in the figure. The reference value P1 is adjusted so as to decrease with the detected voltage value Vs. The relationship between the voltage detection value Vs and the reference value P1 is set so as to conform to the safe operation area of the variable impedance element of the load unit 2, for example.
FIG. 13 shows a configuration example of the integration circuit 31F, but the integration circuit 32F can also be realized by the same configuration.

  As described above, in the electronic load device shown in FIG. 11, the current and power are adjusted so as to conform to the characteristics of the variable impedance element used in the load unit 2 according to the voltage of the load unit 2 detected by the detection unit 5. The upper limit setting signal is corrected. Thus, even when various output voltages are applied to the load unit 2, the upper limit setting signal is corrected so as to match the characteristics of the variable impedance element of the load unit 2 according to the voltage, so that the load unit 2 is normal. It is possible to operate stably in various operating areas. Further, with respect to the performance of the peak value of the instantaneous load and the driving time of the load, it is not necessary to set an extra margin in consideration of the case where a high voltage is applied to the load unit 2, and thus the performance is sacrificed by such a margin. Compared to the case, the larger instantaneous load can be driven for a longer time.

The correction of the upper limit value setting signals L1 and L2 according to the voltage detection value Vs may be performed by adjusting the reference values P1 and P2 as described above, or may be performed by adjusting the time constants τ1 and τ2. . It is also possible to correct upper limit value setting signals L1 and L2 by subjecting the upper limit value setting signals L1 and L2 after integration to signal processing such as addition of an offset or multiplication by a proportional multiplier.
That is, the signal generation unit (3, 3A to 3F) described above has a current or a current so as to conform to the characteristics of the variable impedance element used in the load unit 2 according to the voltage of the load unit 2 detected by the detection unit. The power upper limit setting signal may be corrected. This correction can be realized by, for example, a method of adjusting the reference values P1 and P2 according to the detected value of the voltage of the load unit 2.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.
In the electronic load device according to the first embodiment described above, in order to generate the upper limit setting signal according to the temperature in the signal generation unit, a result obtained by integrating the detection value such as the power of the load with respect to time is used. Yes. In the electronic load device according to the present embodiment, a temperature sensor is used to generate an upper limit setting signal corresponding to the temperature in the signal generation unit.

FIG. 14 is a diagram illustrating an example of the configuration of the electronic load device according to the present embodiment.
The electronic load device shown in FIG. 14 includes a load unit 2, a signal generation unit 3G, a control unit 4, a detection unit 5G, and a temperature sensor 6.
Since the load unit 2, the control unit 4, and the temperature sensor 6 have already been described in relation to the electronic load device shown in FIGS. 1 and 9, only the signal generation unit 3G and the detection unit 5G will be described here.

  The detection unit 5G detects at least one of the current and voltage of the load unit 2. In the example of FIG. 11, the voltage detection unit 52 that detects the voltage of the load unit 2 is provided.

The signal generation unit 3G generates an upper limit setting signal L that sets an upper limit current value of the load unit 2 in accordance with detection results of the detection unit 5G and the temperature sensor 6.
In the signal generation unit 3G, the upper limit current value of the load unit 2 is predetermined as a function of the temperature and voltage of the load unit 2. When the signal generation unit 3G receives the voltage detection value Vs of the load unit 2 by the detection unit 5G and the temperature detection value Ts of the load unit 2 by the temperature sensor 6, based on these detection values and the above function, the load unit An upper limit setting signal L for setting an upper limit current value of 2 is generated.

  For example, the signal generation unit 3G includes a storage unit that stores a data table in which the voltage detection value Vs and the temperature detection value Ts are associated with the upper limit setting signal L. When the voltage detection value Vs and the temperature detection value Ts are input, the signal generation unit 3G reads the upper limit setting signal L corresponding to the input from the data table and outputs it.

  Alternatively, the signal generation unit 3G may include a calculation unit that calculates the upper limit setting signal L using the voltage detection value Vs and the temperature detection value Ts as variables. In this case, when the voltage detection value Vs and the temperature detection value Ts are input, the signal generation unit 3G calculates the upper limit setting signal L corresponding to the input in the calculation unit.

  The signal generation unit 3G is not limited to such a digital circuit, and an analog signal processing circuit that processes the voltage detection value Vs and the temperature detection value Ts with an analog arithmetic circuit and generates the processing result as an analog upper limit setting signal L. Can also be configured.

  As described above, the current and voltage at which the variable impedance element can operate normally are defined as a safe operation region as shown in FIG. 12, for example. This safe operating area generally varies with temperature. In the signal generation unit 3G, the upper limit current value of the load unit is determined as a function of the temperature and voltage of the load unit 2 so as to conform to the safe operation region of the variable impedance element of the load unit 2 that changes according to the temperature. .

As described above, according to the electronic load device of the present embodiment, the upper limit current value of the load unit 2 as a function of the temperature and voltage of the load unit 2 so as to conform to the characteristics of the variable impedance element of the load unit 2. Is predetermined. When the voltage detection value Vs and the temperature detection value Ts of the load unit 2 are obtained, the upper limit current value of the load unit 2 is set based on these detection values and the above function, and the load current is set according to the upper limit value. Is limited.
Therefore, even if the temperature of the load unit 2 rises by flowing a large load current instantaneously, the load current is limited so that the variable impedance element of the load unit 2 can operate normally at that temperature. Even when an instantaneous load larger than the rated value is driven, the load unit 2 can be stably operated in a normal operation region. Therefore, according to the electronic load device according to the present embodiment, it is possible to drive an instantaneous load that is much larger than the conventional one without increasing the size of the device.

In general transistors, in addition to the current, voltage, and temperature of the transistor, the time width (pulse width) of a single pulse current that flows through the transistor, or the ratio of the pulse period to the pulse width in a repetitive pulse current (pulse Duty) is also a variable that defines the safe operation area (see FIG. 12).
Therefore, in the signal generation unit 3G, the upper limit current value of the load unit 2 may be determined in advance as a function of the voltage and temperature of the load unit 2 and as a function of the pulse width or pulse duty of the load current. This can be realized, for example, by providing the above-described data table to which items of pulse width and pulse duty are added.
When the control unit 4 enters an operation mode in which the impedance of the load unit 2 is controlled so that the current waveform of the load unit 2 becomes a single pulse or a periodic pulse train (for example, called a dynamic load mode), the signal generation unit 3G Obtains information on the pulse width and pulse duty from the control unit 4. Then, based on this pulse information, each detection value (Vs, Ts), and a function that determines the upper limit current value, the load current upper limit setting signal L is generated.
In this way, by setting the upper limit current value of the load unit 2 in consideration of the pulse width and pulse duty of the load current, a larger instantaneous load is driven while ensuring stable operation of the load unit 2. It becomes possible.

When the upper limit current value of the load unit 2 is set in consideration of the pulse width and pulse duty of the load current, information on the pulse width and pulse duty is acquired from the control unit 4 as described above. Alternatively, these pieces of information may be detected from the load current.
That is, a pulse detection unit that detects the pulse width of the pulsed current flowing through the load and the period of the pulse train may be provided separately, and the detection result may be given to the signal generation unit 3G.

  As mentioned above, although several embodiment of this invention was described, this invention is not limited only to said form, Various modifications are included.

For example, in the above-described embodiment, the case where the power supply device 1 is a constant voltage power supply is described as an example. .
In this case, the signal generation unit in each of the embodiments described above generates an upper limit setting signal for setting the upper limit value of the voltage or power of the load unit 2. The control unit controls the impedance of the load unit 2 so as not to exceed the upper limit of the voltage or power set in the upper limit setting signal.

  When the power supply device 1 is a constant current power supply, in the electronic power supply device shown in FIGS. 7 and 8, the current detection unit 51 of the detection units 5B and 5C is replaced with a voltage detection unit 52. Thereby, similarly to the electronic power supply device shown in FIG. 1, it is possible to limit the load voltage (or load power) according to the temperature.

  When the power supply device 1 is a constant current power supply, in the electronic load device shown in FIG. 14, the voltage detection unit 52 of the detection unit 5G is replaced with the current detection unit 51. In this case, in the signal generation unit 3G, the upper limit voltage value of the load unit 2 is a function of the temperature and current of the load unit 2 (or the pulse width or pulse of the voltage of the load unit 2 to the temperature and current of the load unit 2). It is predetermined (as a function of duty added as a variable). When the signal detection unit 3G receives the current detection value Is of the detection unit 5G and the temperature detection value Ts of the temperature sensor 6, the signal generation unit 3G receives these detection values (or these detection values and pulse width information or pulse duty information). Based on the above function, an upper limit setting signal L for setting the upper limit voltage value of the load unit 2 is generated.

  In the first embodiment described above, the upper limit setting signal is generated by performing predetermined integration on the detection value of the detection unit, but the present invention is not limited to this. For example, after performing various signal processing suitable for actual application, such as giving an appropriate offset to the detection value of the detection unit or multiplying by an appropriate proportionality coefficient, a predetermined integration is performed to generate an upper limit setting signal. Also good.

  In the present invention, each of the above-described embodiments may be implemented independently, or any combination of these components may be performed.

  The electronic load device of the present invention is not limited to a general power supply device, and can be widely applied to load tests of various devices that can output power as a power source, such as a primary battery, a secondary battery, and a power generation device.

It is a figure which shows an example of a structure of the electronic load apparatus which concerns on 1st Embodiment. It is a figure which shows an example of a structure of a load part and a control part. It is a figure which shows an example of a structure of an integration circuit. It is a figure which illustrates the time change of the load power and the time change of the temperature of a load part at the time of changing the setting value of load current in steps in the electronic load device shown in FIG. It is a figure which illustrates the 1st modification of the electronic load apparatus which concerns on 1st Embodiment. It is a figure which shows the example of the time change of load power in case load power is restrict | limited according to an upper limit setting signal. It is a figure which illustrates the 2nd modification of the electronic load apparatus which concerns on 1st Embodiment. It is a figure which illustrates the 3rd modification of the electronic load apparatus which concerns on 1st Embodiment. It is a figure which illustrates the 4th modification of the electronic load apparatus which concerns on 1st Embodiment. It is a figure which illustrates the 5th modification of the electronic load apparatus which concerns on 1st Embodiment. It is a figure which illustrates the 5th modification of the electronic load apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the safe operation area | region of a transistor. It is a figure which shows an example of a structure of the voltage generation circuit in the integration circuit of the electronic load apparatus shown in FIG. It is a figure which shows an example of a structure of the electronic load apparatus which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power supply device, 2 ... Load part, 3, 3A, 3B, 3C, 3D, 3E, 3F, 3G ... Signal generation part, 4 ... Control part, 5, 5B, 5C, 5G ... Detection part, 6 ... Temperature sensor

Claims (8)

A load section capable of controlling impedance;
A detection unit for detecting at least one of the current, voltage and power of the load unit;
A signal generation unit that generates a plurality of upper limit setting signals that are signals according to the temperature of the load unit and set at least one upper limit of the current, voltage, and power of the load unit;
A control unit that controls the impedance of the load unit so that at least one of the current, voltage, and power of the load unit does not exceed the upper limit set by the plurality of upper limit setting signals;
Have
The signal generation unit generates the plurality of upper limit setting signals according to a result obtained by integrating a difference between a detection value of the detection unit and a plurality of predetermined reference values with respect to time with different time constants;
Load device. A temperature sensor that converts the temperature of the load section into an electrical signal and outputs the electrical signal;
The signal generator is configured so that the upper limit is lowered when the temperature of the load unit is high, and the upper limit is increased when the temperature of the load unit is low, according to the output signal of the temperature sensor. Set a predetermined reference value,
The load device according to claim 1 . A temperature sensor that converts the temperature of the load section into an electrical signal and outputs the electrical signal;
The signal generation unit responds to an output signal of the temperature sensor so that the time constant is shortened when the temperature of the load unit is high and the time constant is long when the temperature of the load unit is low. To set the predetermined reference value,
The load device according to claim 1 or 2 . The signal generation unit corrects the upper limit setting signal of the current and / or power of the load unit according to the voltage detected by the signal detection unit,
The load apparatus in any one of Claims 1-3 . When the signal generation unit sets the upper limit setting signal, the upper limit value indicated by the upper limit setting signal is adapted to the safe operation region of the variable impedance element of the load unit,
Correcting the reference value according to the voltage detected by the detection unit;
Or
Correcting the time constant according to the voltage detected by the detector;
Or
An offset is added to the upper limit setting signal according to the voltage detected by the detection unit,
Or
Multiplying the upper limit setting signal by a proportional multiplier according to the voltage detected by the detection unit;
The load device according to claim 4. The signal generator is
A first differential operational amplifier having a first input terminal, a second input terminal, and an output terminal; and a first input terminal of the first differential operational amplifier; An input resistance element for inputting a signal indicating the detected power to the first input terminal;
A reference voltage generating circuit connected to a second input terminal of the first differential operational amplifier and outputting a voltage corresponding to the reference power;
A capacitor provided between an output terminal of the first differential operational amplifier and the first input terminal;
Have
The time constant is defined by the resistance value of the input resistance element and the capacitance value of the capacitor,
The first differential operational amplifier, the input resistance element, and the feedback capacitor cooperate to apply to the first input terminal and the second input terminal of the first differential operational amplifier. Calculating and amplifying the difference of the generated voltage, and integrating the amplified difference signal with the time constant to generate the upper limit setting signal ,
The load device according to any one of claims 1 to 5. The controller is
A voltage generating circuit for generating a voltage for setting a target value of a load current of the power supply device;
A second differential operational amplifier circuit having first and second input terminals and an output terminal connected to a control input terminal of the variable impedance element included in the load section;
The second differential calculation is performed by limiting an upper limit value of a voltage for setting a target value of the load current generated by the voltage generation circuit according to the upper limit setting signal output from the signal generation unit. A limit circuit input to the first input terminal of the amplifier circuit;
A resistance element for detecting a current flowing in the variable impedance element included in a load unit capable of controlling the impedance;
Have
Connected to a second input terminal of the second differential operational amplifier circuit at a connection point between the resistance element and the output of the variable impedance element;
The transistor, the second differential operational amplifier circuit, and the resistance element constitute a constant current circuit,
The second differential operational amplifier circuit obtains a difference between an output signal of the limit circuit applied to the first input terminal and a terminal voltage of the resistance element applied to the second input terminal. And applying the amplified difference signal to the control input terminal of the transistor,
The load device according to any one of claims 1 to 5. The detector is
A current detection unit for detecting a current of the load unit;
A voltage detection unit for detecting a voltage of the load unit;
A multiplier for calculating power by multiplying a current detection signal by the current detection unit and a voltage detection signal by the voltage detection unit;
Having
The load device according to claim 1.

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